Denver Zoo has a history of opening mega-exhibit complexes every few years instead of smaller, annual improvements. Some zoos (like Omaha and Columbus) seem to debut a brand new animal habitat each year, but Denver residents wait patiently for many years and then suddenly an ultra-expensive, huge zone of the zoo is transformed.
Major Exhibits (from the past 36 years):
Bird World - 1975 (It cost $1.25 million and at the time was regarded as one of the best bird complexes in America. Even today Denver has around 200 species of birds in its collection.)
Mountain Sheep Habitats - 1979 ($400,000 and featuring Dall sheep and Bighorn sheep)
Northern Shores - 1987 (3 acres of polar bears, sea lions, harbor seals, Arctic wolves, Arctic foxes, river otters, waterfowl)
Tropical Discovery - 1993 ($10 million rainforest building with a few mammals but loads of reptiles, amphibians, fish and invertebrates plus over 200 plant species)
Primate Panorama - 1996 (7 acres and an impressive 30 species of primates from 3 different continents; some additional animal exhibits as well)
Predator Ridge & Entrance Complex - 2004 ($27 million, 14-species area; rotation exhibits for lions, spotted hyenas and African wild dogs; new entrance area and several other smaller animal exhibits)
Asian Tropics - 2012 ($50 million, 10 acre complex; rotation exhibits for Asian elephants (possibly up to 12 in the future), Malayan tapirs and Indian rhinos; fishing cats, clouded leopards, fruit bats; sarus cranes, small-clawed otters, gibbons, etc).